<%@ page contentType="image/jpeg"
	import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*,javax.servlet.http.*"%><%!
//http://www.xiuce888.cn/2009/05/12/javalangillegalstateexception-getoutputstream-has-already-been-call/	
	Color getRandColor(int fc, int bc) {
        Random random = new Random();
        if (fc > 255)
            fc = 255;
        if (bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }%><%
    response.setHeader("Pragma", "No-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setDateHeader("Expires", 0);

    int width = 60, height = 20;
    BufferedImage image = new BufferedImage(width, height,
            BufferedImage.TYPE_INT_RGB);

    Graphics g = image.getGraphics();

    Random random = new Random();

    g.setColor(getRandColor(200, 250));
    g.fillRect(0, 0, width, height);

    g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

    g.setColor(getRandColor(160, 200));
    for (int i = 0; i < 155; i++) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(12);
        int yl = random.nextInt(12);
        g.drawLine(x, y, x + xl, y + yl);
    }

    String sRand = "";
    for (int i = 0; i < 4; i++) {
        String rand = String.valueOf(random.nextInt(10));
        sRand += rand;

        g.setColor(new Color(20 + random.nextInt(110), 20 + random
                .nextInt(110), 20 + random.nextInt(110)));

        g.drawString(rand, 13 * i + 6, 16);
    }
    session.setAttribute("authentication", sRand);
    g.dispose();
    ImageIO.write(image, "JPEG", response.getOutputStream());
%>